PROJECT SUMMARY/ABSTRACT Candidate & Fellowship Training Plan: Dr. Kamil Faridi received his MD from Duke University Medical School and completed residency in internal medicine at Johns Hopkins Hospital. He is currently a third-year cardiology fellow at Beth Israel Deaconess Medical Center (BIDMC) and is enrolled in an MSc in Epidemiology program at the Harvard T.H. Chan School of Public Health. He is also a research fellow at the Richard A. and Susan F. Smith Center for Outcomes Research in Cardiology. He maintains 75% protected time to conduct clinical research on the BIDMC institutional T32 grant. Through implementation of this 2-year research proposal with supervised mentorship and coursework, Dr. Faridi will gain the necessary skills and experience for subsequent application to a K23 award or equivalent. The candidate?s long-term goal is to become an R01- funded investigator in applied outcomes research, focusing primarily on coronary artery disease. Environment: The candidate will be mentored by Dr. Robert Yeh (primary mentor/sponsor), Associate Professor of Medicine at Harvard Medical School and Director of the Smith Center for Outcomes Research in Cardiology, and Dr. Changyu Shen (co-sponsor), Director of Statistics at the Smith Center and Associate Professor of Medicine at Harvard Medical School. Both sponsors are internationally recognized leaders in their fields and provide complementary expertise relevant to the research and training of the applicant. Dr. Yeh has an established track record of successfully mentoring clinical investigators and has committed research funding to complete the proposed work. The combined resources of the Harvard medical institutions will provide a rich and productive environment for Dr. Faridi?s career development through a combination of didactics, seminars, research meetings, and conference presentations. Research: Frailty is a strong predictor of morbidity and mortality but is rarely addressed in research studies of patients with coronary artery disease (CAD). Frailty and CAD are also common among older adults, and evidence to guide clinicians in treating patients with these conditions is urgently needed. One area of uncertainty is appropriate use of dual antiplatelet therapy (DAPT) following percutaneous coronary intervention (PCI). Current evidence suggests that extended duration of DAPT beyond 12 months following PCI reduces risk of cardiovascular events while increasing risk of bleeding. However, the effects of frailty on risks and benefits of extended duration DAPT are currently unknown. By using linkage of a multicenter randomized trial (the DAPT Study) with Medicare claims data, Aim 1 will assess the risk of adverse outcomes for frail vs. non- frail patients with CAD after PCI. Aim 2 will determine modification of treatment effects of extended duration DAPT based on frailty status. Lastly, Aim 3 will assess whether patients with CAD in a clinical trial have similar frailty prevalence and outcomes compared to older adults in real-world practice. This proposal will improve our understanding of frailty and assist with clinical decision-making for patients with CAD following PCI.